If i understand things right, some additional hardware is needed to get an audio-signal into iPod touch via the dock. Is there (or will there be) any possibility (e.g. some driver) to route the audio-signals to the USB-Connector cable?

Ok, I'm confused. Using a iPhone 3gs I want to send signal generator out and use the built-in mic with the octave analyzer simultaneously. If I use a standard doc output or the earphone output, the signal is routed directly back in to the corresponding input. To equalize speaker system, I need to be able to output pink noise while using the analyzers simultaneously. Is this possilble? Maybe with the Alesis ProTrack? Thanks in advance!

If you plug a stereo cable into the headset jack, the selected output will be headphones and the selected input will be the built-in microphone. The headset input won't be selected unless you connect a suitable load to the input channel of the headset jack (which requires a four-conductor mini-plug).

However, based on some measurements I made on June 19 (see the blog), I don't recommend using anything other than the dock input (line input) of the iPhone 3G S for frequency response measurements (unless you don't care about frequencies below 200 Hz).

Ben, thanks for your response. At first I could not reconcile your first paragraph as the application would not select mic input with signal generator going out the headset jack. However, I tried sliding the stereo (tip/ring/sleeve) connector out a fraction of an inch and behold, the expected behavior manifested itself. Just what I needed. Must be something shorting if the connector is not seated exactly right. Thanks again. Kent

I would like to use SSP for equalizing my car audio system. My iPhone (original) connects to the car system using a dock connector - I have no aux jack input. Ideally I would use SSP to generate pink noise to the dock output while simultaneously capturing input from the Apple headset microphone (original version), or another mic attached to the headset jack.

I performed a simple experiment to see if this might be possible. I first setup my iPhone to produce music on the Apple headset, then connected the car's dock connector. At that point the desired result was achieved, i.e., the music switched from playing on the headset to the car's stereo system. But I am unable to determine if the Apple headset micrphone could be tapped by SSP in this configuration. Would this work, or would the iPhone input also be switched to the dock?

Of course the other option would be to play a CD containing pink noise from my CD player while capturing input using the headset mic.

The iPhone will prevent you from using the headset input and the dock output at the same time. However, if your goal is to use the 1/3-octave spectrum analyzer for equalization, then it may be just as well to play pink noise from a CD, as you suggested.

The original iPhone has the flattest frequency response on its headset input, so I would recommend the ThumbTacks microphone for your setup.

So it appears Apple allows the dock input to be used simultaneously with the headphone jack output, but not the other way around.

That's right. The iPhone (and 2G iPod touch) can tell the differences between headphones (or a stereo connector) and a headset (a four-conductor connector). When the headset is used, input and output are routed through that single jack. If headphones are used, the iPhone looks for input from another source, so you can use dock input and headphone output.

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Thanks for the pointer to ThumbTacks. Should this microphone be oriented vertically for EQ measurements?

The microphone is omnidirectional, but the iPhone (and your hand) will obviously affect that. A vertical orientation, then, should be fine.

Thanks Ben,i've been trying to do an analog line in into the iphone dock connector but it's not working. line outis working fine though but needed some jumper between pins besides the documented output pins.Is there an undocumented trick to make the line in work?Thanksfrancois

It was noted on the blog that the Belkin TuneTalk Stereo works with an iPhone 3GS running OS 3.0.1. Is it known to work under OS 3.1.2?

I had a MacAlly iVoiceIII working on an original iPhone running OS 3.0.1, but when I upgraded to 3.1.2, I received two errors messages. After the second one was displayed stating that "This accessory is not supported by iPhone", the device was disabled. I observe the same behavior on a 3GS running OS 3.1.2.

I'm considering trying a TuneTalk with SignalScope Pro, but would like some assurance that it will work before I purchase it.